TLS Online TPP Program

#Id: 8284


During hydrophobic interaction, the non-polar molecules come together, releasing some of the ordered water molecules in the clathrate structure and thus increasing entropy.
This is a thermodynamically favourable process (dG < 0), even though it is endothermic (dH > 0) because more hydrogen bonds are broken than are made.

#Unit 1. Molecules and their Interaction Relevant to Biology #Stablizing interactions (Van der Waals, electrostatic, hydrogen bonding, hydrophobic interaction) #Part B Pointers
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TLS Online TPP Program

#Id: 7852

#Unit 1. Molecules and their Interaction Relevant to Biology

The pyranose forms of the sugars are more stable than the furanose forms in solution.


TLS Online TPP Program

#Id: 7853

#Unit 1. Molecules and their Interaction Relevant to Biology

Thus, D glucose in aqueous solution exists as an equilibrium mixture of 5 compounds. The pyranose form predominates in solution.

aD glucofuranose (0.5%)

aD-glucopyranose (37%)

aldehydo- -glucose (0.003%)

bD-glucofuranose (0.5%)

bD-glucopyranose (62%)

TLS Online TPP Program

#Id: 7854

#Unit 1. Molecules and their Interaction Relevant to Biology

The optical activity of a stereoisomer is expressed quantitatively by its optical rotation.
The number of degrees by which plane-polarized light is rotated on passage through a given path length of a solution of the compound at a given concentration.

TLS Online TPP Program

#Id: 7855

#Unit 1. Molecules and their Interaction Relevant to Biology

Optical rotation

TLS Online TPP Program

#Id: 7856

#Unit 1. Molecules and their Interaction Relevant to Biology

When equal amounts of extrorotatory and levorotatory isomers are present, the resulting mixture becomes optically inactive because the optical activities of each isomer cancel each other.
Such a mixture is called a racemic or dl-mixture or (±)-conglomerate and this process of converting an optically active compound into the racemic modification is known of racemization. 

TLS Online TPP Program

#Id: 7857

#Unit 1. Molecules and their Interaction Relevant to Biology

A freshly-prepared aqueous solution of α-D-glucose, has a specific rotation

A fresh solution of β-D-glucose, on the other hand, has a rotation value of +18.7°